Modification of hemicellulose polysaccharides during ripening of postharvest banana fruit

Alcohol-insoluble residues (AIRs) from postharvest banana fruits at five ripening stages were extracted and isolated. The AIR was fractionated with 1 M KOH or 4 M KOH to obtain hemicellulose polysaccharides 1 (HC1) and 2 (HC2), respectively, and their content, molecular-mass, monosaccharide composition and glycosidic linkages were evaluated. HC1 yield decreased significantly from 126.95 to 21.14 mg/g on fresh weight basis during fruit ripening, but HC2 yield increased and then decreased. Concomitantly, the molecular-mass of HC1 and HC2 decreased obviously, indicating that depolymerization occurred. Moreover, the major monosaccharide compositions were identified as glucose and xylose. The GC–MS analysis further revealed that HC1 and HC2 had a 1,4-linked glucose backbone. During fruit ripening, the molar percentage of 1,4-linked Glcp residues increased in HC1, but decreased slightly in HC2. Overall, this study indicated that the modification and depolymerization of hemicellulose polysaccharides were responsible for banana fruit softening.     

Pectin Changes in Ripening Cherry Fruit

Pectin solubilization was studied during ripening of cherry fruit. Pectic materials were isolated at specific stages during development. The proportion of alcohol-insoluble-material decreased on a fresh weight basis with ripeness, but increased per fruit. Pectic substances were divided into water-, oxalate- and acid-soluble fractions. The oxalate-and water-soluble part increased as acid-soluble components decreased. Water- and acid-soluble fractions contained many more neutral sugar residues than the oxalate-soluble fraction. Changes in individual sugars indicated the major alterations were the degradation of galactan and the absence of arabinan solubilization in acid-soluble pectic substance. Size exclusion chromatography showed absence of pectin depolymerization during ripening, indicating that fruit softening does not depend on pectin depolymerization.     

Effect of 1-methylcyclopropene on ripening of postharvest persimmon (Diospyros kaki L.) fruit

Postharvest persimmon fruit (Diospyros kaki L. cv. Qiandaowuhe) was stored at 20 °C after being exposed to 3 μl l⁻¹ 1-methylcyclopropene (1-MCP) for 6 h or not (control). Several parameters (firmness, respiration and ethylene production, pectic substances and cell wall hydrolysis enzymes activities) were examined to determine the efficacy of 1-MCP treatment in delaying persimmon fruit ripening. Results showed that ‘Qiandaowuhe’ persimmon fruit displayed a typical climacteric pattern of respiration and ethylene production. Peak CO₂ production and ethylene production was observed on the fourth day. Fruit softening was accompanied by a progressive increase in water-soluble pectic substances (WSP) and a progressive decrease in chelator-soluble pectic substances (CSP) and alkali-soluble pectic substances (ASP). The activities of pectinmethylesterase (PME) and polygalacturonase (PG) started increasing sharply and reached a maximal value on days 4 and 6, respectively, and then decreased slowly. 1-MCP treatment delayed the onset of climacteric ethylene production and respiration in persimmon fruit, and also significantly retarded the activities of PME and PG during ripening at 20 °C. Consistent with the activity trends of cell wall hydrolysis enzymes, 1-MCP treatment also delayed the depolymerization of CSP and ASP and reduced the increase of WSP compared with the control fruit. Thus, application of 1-MCP can greatly extend the postharvest life of ‘Qiandaowuhe’ persimmon fruit.     

Characterization of the pectic polysaccharides from pumpkin peel

The alcohol insoluble polysaccharide (AIP) was extracted from pumpkin (Cucurbita moschata Duch) peels, and they were fractionated subsequently into water soluble pectic substance (WSP), EDTA soluble pectic substance (ESP) and alkali soluble pectic substance (ASP) fractions. ASP fraction (24.78 and 46.07 g/100 g) contained the highest total sugar and uronic acid contents compared with WSP (17.78 and 4.89 g/100 g) and ESP (18.43 and 23.99 g/100 g) fractions. WSP fraction had 2 peaks with a small one close to 205 kDa and a major one close to 13 kDa, while ESP and ASP fractions had 3 peaks with higher molecular weight distributions than WSP. The sugar peaks in the ion exchange chromatography were detected in a low concentration of ammonium acetate buffer, but uronic acid peaks were detected in a high concentration of ammonium acetate buffer and 0.2 mol/l NaOH. ESP had higher glucose retardation effect than that of WSP and ASP, while WSP and ASP had higher bile acid retardation effects than that of ESP. AIP fractions activated growth in Lactobacillus brevis, Bifidobacterium bifidum and Bifidobacterium longum, whereas they inhibited growth in Escherichia coli and Clostridium perfringens in RCM medium.     

SOFTENING AND BIOCHEMICAL CHANGES OF SAPOTE MAMEY FRUIT (POUTERIA SAPOTA) AT DIFFERENT DEVELOPMENT AND RIPENING STAGES

We investigated some of the physicochemical and biochemical factors associated with flesh softening of sapote mamey fruit during development and ripening. The activities of pectinmethylesterase (PME), polygalacturonase (PG) and β‐galactosidase (β‐GAL) enzymes were measured in fruits harvested at different development stages, and postharvest in two production seasons. The textural changes were most noticeable at the preclimacteric stage in ripening fruit. The water‐soluble pectin (WSP) increased at a different rate than firmness decreased. No correlation between PG or PME activity and changes in firmness was observed in ripening fruits, though a low correlation was seen between β‐GAL activity and softening in climacteric stage. Greatest loss of firmness occurred in climacteric stage. Fruit pulp softening was not dependent on a single enzyme activity.     

Effect of high pressure/high temperature processing on cell wall pectic substances in relation to firmness of carrot tissue

Thermal processing for food preservation results in undesired softening of fruits and vegetables. To explore the potential of high pressure sterilization in food processing, the effects of combined high pressure/high temperature (HP/HT) treatments on carrot pectic polysaccharides and the related textural properties were investigated and compared with that of samples thermally processed at atmospheric pressure. Disks of fresh carrot (Daucus carota var. Yukon) tissue were subjected to three different treatments (80 °C–0.1 MPa, 100 °C–0.1 MPa and 80 °C–600 MPa) for varying time intervals. Subsequently, the residual texture and microstructural changes of the carrots were evaluated. Alcohol-insoluble residues were prepared from the samples and sequentially fractionated with water, cyclohexane-trans-1,2-diamine tetra-acetic acid (CDTA) and Na₂CO₃ solutions. Thermal treatments at 0.1 MPa caused extensive tissue softening. This was marked by increased cell separation, an increase in water soluble pectin (WSP) paralleled by a decrease in chelator (CSP) and sodium carbonate (NSP) soluble pectin. HP/HT treated carrots showed minimal softening and negligible changes in intercellular adhesion. This was accompanied by a significant reduction in the degree of methyl esterification of pectin, low WSP in contrast to the high CSP and NSP fractions, minor changes in the different pectin fractions during treatment, and a substantial amount of pectin in the fractionation residue. There was a clear difference between HP/HT and thermally processed carrot pectin; HP/HT showing pronounced texture preservation.     

硬溶质型桃果实成熟过程中细胞壁多糖降解特性及其相关酶研究

以硬溶质型桃‘晚湖景’为试材,研究细胞壁多糖降解以及细胞壁多糖降解相关酶对硬溶质型桃果实成熟软化的影响。结果表明:硬溶质型桃果实成熟过程中,CDTA-1果胶含量上升,两种Na2CO3溶性果胶含量在成熟末期减少率分别为22.5%和27.4%。KOH溶性果胶含量在整个成熟过程中变化不明显。果实CDTA、Na2CO3组分中果胶多糖主链的断裂、半纤维素和纤维素组分中阿拉伯糖和半乳糖的降解主要发生在成熟末期;β-半乳糖苷酶(β-Gal)与桃果实成熟软化启动密切相关,多聚半乳糖醛酸酶(PG)和纤维素酶(Cx)对桃果实成熟后期快速软化起重要作用。Na2CO3-1溶性果胶多糖的降解与硬溶质型果实采后软化密切相关,KOH-1、KOH-2半纤维素多糖的降解可能促进硬溶质型桃果实成熟软化进程,富含半乳糖醛酸的果胶多糖主链的断裂以及果胶、半纤维素、纤维素中阿拉伯糖、半乳糖等中性糖的降解都可能是果肉软化的重要因素,并有多种多糖降解酶参与其中。     

Isolation and characterisation of pectic substances from murta (Ugni molinae Turcz) fruits

Cell walls polysaccharides from murta fruit (Ugni molinae Turcz), an endemic Chilean species with relevant food uses, were fractionated by water, ammonium oxalate, hot diluted HCl and cold diluted NaOH extractions. The polysaccharide fractions were analysed for monosaccharide composition and physicochemical properties. Pectic substances were found in all extracts, but mainly in the oxalate and acid soluble fractions, in which they appear as homogalacturonan polymers. Murta pectin was further extracted by hot diluted acid treatment using industrial conditions, yielding 30% by weight of dry fruit. The polymer showed similar composition and physicochemical properties to those of commercial citrus pectin, presenting a galacturonic acid content of 70.9% (w/w), a molecular weight of 597 kDa, and a methoxylation degree of 57%. The FT-IR spectrum of murta pectin suggests the presence of ferulic acid residues on its structure and the NMR analysis confirmed the structure of this polysaccharide. It is concluded that murta fruit can be considered as a valuable source of high quality pectin.     

Pectin Transitions During Blueberry Fruit Development and Ripening

Quantitative and qualitative changes in the pectin composition of “Bluetta” blueberries were determined during fruit development between 30 and 57 days after full bloom. The contribution of alcohol insoluble solids (AIS) to the total fruit mass decreased threefold with maturation, while the pectin contribution decreased twofold in the fruits. Within the AIS fractions during ripening there was a reduction in dilute alkali soluble pectin (DASP) from about 65% to 20% of the AIS. A corresponding increase was observed in water soluble pectin (WSP), from about 20% to 60%, while chelator soluble pectin (CSP) increased slightly.     

Physico-chemical characterization of alkaline soluble polysaccharides from sugar beet pulp

We studied the global (i.e. overall) structure of microwave-assisted alkaline soluble polysaccharides (ASP) isolated from fresh sugar beet pulp. The objective was to minimize the disassembly and possibly the degradation of these polysaccharides during extraction. Prior to ASP microwave-assisted extraction (MAE), pectin was removed and isolated by MAE. Two sub fractions, ASP I and ASP II were isolated. ASP I had about the same ratio of anhydrogalacturonate (AGA) to neutral sugar (NS) by percentage weight (%wt) whereas ASP II had about twice as much AGA to NS by %wt. Unlike the sugar beet pectin isolated, the degree of methyl esterification of AGA in both ASP fractions was very low. Arabinose was the most abundant neutral sugar followed by either rhamnose or galactose. For optimum sample 10/100/30, High Performance Size Exclusion Chromatography with molar mass and viscometric detection revealed that both ASP fractions are about 100,000 Da in M_w and about 10 and 16 nm in Rg_z, respectively. ASP I and ASP II had weight average intrinsic viscosities of 0.31 and 0.33 dL/g respectively and their Mark–Houwink exponents indicated that they are relatively compact in shape. Molar Mass distributions of ASP appeared to be bimodal in shape. Atomic Force Microscopy (AFM) images of ASP I revealed a bimodal distribution of small and large compact asymmetric subunits when a 0.1 μg/mL air dried, aqueous solution was deposited on freshly cleaved mica and imaged. When the solution concentration was 25 μg/mL in ASP I, the subunits appeared to aggregate into skeletal structures whereas ASP II only formed compact asymmetric structures. Unlike AFM images of sugar beet pectin previously imaged, neither ASP I nor ASP II formed network structures at higher concentrations. Both ASP I and II were found to emulsify orange oil.     

杏鲍菇菇头多糖的结构鉴定及生物活性评价

采用热水浸提法从杏鲍菇菇头中提取粗多糖,采用凝胶渗透色谱-示差折光指数-十八角激光散射联用技术测定粗多糖的分子质量分布,气相色谱法测定单糖组成,气相色谱-质谱联用法测定糖苷键链接方式,2,2’-联氨-双-3-乙基苯并噻唑啉-6-磺酸（2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid),ABTS）法测定抗氧化性,3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐法测定体外抗肿瘤活性,动物实验法检测体内抗肿瘤活性。结果表明：该粗多糖主要由葡萄糖组成（占84.4%）;其分子质量分布较广,4 个主峰分子质量分别为3.816×107、2.010×106、4.572×105 Da和1.849×105 Da;糖苷键主要链接方式为1,3-糖苷键（占42.7%）和1,6-糖苷键（占35.5%）;当质量浓度为5 mg/mL时,粗多糖对ABTS阳离子自由基的抑制率为70.9%。动物实验表明,以200 mg/（kg·d）剂量连续灌胃12 d后,粗多糖对荷瘤小鼠（宫颈癌U14）的抑瘤率可达39.84%。     

Structure of a galactoarabinoglucuronoxylan from tamarillo (Solanum betaceum), a tropical exotic fruit,and its biological activity

Tamarillo (Solanum betaceum) is a tropical exotic fruit whose polysaccharides were extracted from the ripe pulp. After various purification steps, homogeneous fractions (designated PTW, STK-1000R and PF) were analyzed by sugar composition, HPSEC, methylation and NMR spectroscopy analysis. The results showed that the fraction PTW consisted of a linear arabinan with (1 → 5)-linked α-l-arabinofuranosyl units. Fractions designated as STK-1000R and PF contained galactoarabinoglucuronoxylans, with (1 → 4)-linked β-d-Xylp residues in the backbone, carrying branches exclusively at O-2. The polysaccharide in STK-1000R is less branched than that in the PF fraction (∼20.0% and 36.5%, respectively), with side-chains formed by (1 → 5)-linked α-l-Araf residues and (1 → 4)-linked α-d-GlcpA residues and with non-reducing end units formed by α-l-Araf, β-Arap, β-d-Galp, α-d-GlcpA and 4-O-Me-α-d-GlcpA. Intraperitoneal administration of the STK-1000R fraction in mice significantly reduced the number of abdominal constrictions induced by 0.6% acetic acid and the inflammatory phase of nociception induced by 2.5% formalin, indicating that that fraction has an antinociceptive effect on inflammatory pain models.     

Diverse metabolism of cell wall components of melting and non‐melting peach genotypes during ripening after harvest or cold storage

The mode of change in a range of physiological, physicochemical and biochemical parameters during fruit ripening between distinct peach genotypes (Prunus persica L. Batsch) after cold storage for up to 4 weeks was determined. The nectarine cultivar ‘Caldesi 2000’ was selected as a genotype with melting flesh (MF) characteristic (fruits characterized by extensive flesh softening during ripening) and the cultivar ‘Andross’ as a genotype with non‐melting flesh (NMF) characteristic (fruits characterized by limited flesh softening during ripening). Flesh firmness, ethylene production, physicochemical and biochemical properties of the cell wall were determined and significant differences between the fruits of the two genotypes were recorded. Fruits of the NMF genotype were characterized by higher tissue retention and ethylene production during their ripening, higher content of uronic acids, as well as higher capacity for calcium binding in the water‐insoluble pectin fraction compared with fruits of the MF genotype. Additionally, the ripening of MF‐type fruits was characterized by higher losses of neutral sugars, especially those of arabinose and galactose than the NMF‐type fruits and these losses were more intense after extended cold storage periods. In fruits of the NMF genotype the decreased activity of pectin methyl esterase (PME) combined with higher levels of calcium in the water‐insoluble pectin fraction possibly provided less substrate for polygalacturonase (exo‐, endo‐PG) activity and less solubility of cell wall pectin compared with fruits of the MF genotype. Overall, the data indicate the existence of a wide range of diverse metabolic pathways during fruit ripening of fresh fruits with MF and NMF characteristics. Copyright © 2005 Society of Chemical Industry     

苹果发育过程中细胞壁代谢及果肉质地的变化

以质地存在差异的“蜜脆”、“嘎拉”、“倭锦”、“鸡冠”4 个品种的苹果为材料,分析了果实发育过程中硬度、脆度和单果质量的变化,以及细胞壁中果胶、纤维素、半纤维素的含量和多聚半乳糖醛酸酶（polygalacronase,PG）、果胶甲酯酶（pectinmethylesterase,PME）、纤维素酶（carboxymethycellulase,Cx）、β-半乳糖苷酶（β-galactosidase,β-Gal）活性的变化,以期找到品种间质地差异的主要因素。结果表明：果实发育过程中果实硬度降低、脆度变小、感官脆度增大,细胞壁各个组分的含量在4 个品种中均呈下降趋势;在成熟果实中,脆性较好的品种果实中纤维素含量较低,水溶性果胶（water soluble pectin,WSP）含量较高,硬度低的品种果实中离子结合果胶（ionic soluble pectin,ISP）含量较高;PG、β-Gal在高脆品种“蜜脆”、“嘎拉”中活性较高,而Cx、PME活力在各品种间无明显差异。认为WSP、ISP和纤维素含量的差异以及PG和β-Gal活性的差异是形成苹果果实质地差异的关键因素。     

Textural Changes of Yellow Peach in Pouches Processed by High Hydrostatic Pressure and Thermal Processing During Storage

Textural changes of yellow peach in pouches (YPP) treated by high hydrostatic pressure (HHP) and thermal processing during storage at 4?±?1 °C and 25?±?1 °C for 180 days were studied. Hardness, syrup viscosity, pectin compositions, and cell structure of YPP samples were evaluated in this study. The hardness of YPP stored at 4?±?1 °C exceeded 50–70 % as compared to those stored at 25?±?1 °C. Moreover, the higher flesh hardness and lower syrup viscosity were obtained at longer pressure-holding time of HHP processing. Water-soluble pectin (WSP), sodium carbonate-soluble pectin (NSP), and total pectin contents in flesh decreased, while chelate-soluble pectin (CSP) in flesh and water-soluble pectin in syrup (WSPS) increased after 180 days storage. The texture degradation in YPP was mainly caused by solubilization and depolymerization of WSP and NSP. The temperature of 4?±?1 °C inhibited pectin degradation and delayed the softening of flesh and the increase of syrup viscosity more effectively than 25?±?1 °C. Comparing with the flesh tissue microstructure of HHP-processed YPP stored at 25?±?1 °C, better cell structures of YPP were retained during storage at 4?±?1 °C. Since the breakdown of intercellular cementing pectin was obviously delayed at lower storage temperature, thus cell wall loosening and distortion were prevented.     

Extraction and structural identification of alkali-soluble polysaccharides of longan (Dimocarpus longan Lour.) fruit pericarp

Two alkali-soluble polysaccharide fractions (ASPs I and II) were extracted from longan fruit pericarp in this work. The results of chemical composition indicated that ASP I and II fractions comprised mainly of polysaccharides, proteins and lignins. Four monosaccharides, namely Xyl, Ara, Glc and Gal, were identified for both ASPs I and II. Xyl was the dominant monosaccharide in the two alkali-soluble polysaccharides with relative molar percentages of >60%. It constructed the backbone in combination with Ara for both ASPs I and II. The analysis of glycosidic linkage indicated that Xyl had two linkages,→3)-Xyl-(1→ and →3, 4)-Xyl-(1→. The substitution at C-4 position indicated that Xyl was of pyranose structure. The infrared spectra of ASPs I and II showed the characteristic bands at approximate 897 cm^− 1 which indicated the β-linkage configuration of Xyl.

Industrial relevance

Hemicellulose has been suggested as an important polysaccharide with good pharmaceutical properties, including immune modulation and anti-cardiovascular diseases. In this work, alkali-soluble polysaccharides were extracted from longan fruit pericarp and fractionated. The structural characteristics were identified by gas chromatography/mass spectrometry and infrared spectrophotometry. The results will be helpful for application of hemicellulose in functional food industry.     

Pectic polysaccharides of mango (Mangifera indica L): structural studies

Pectic polymers of raw and ripe mango fruits revealed several distinct fractions upon diethylaminoethyl‐cellulose chromatography. Fraction I, the arabinogalactan, had a relative ratio of 3:1 for galactose and arabinose, while the two rhamnogalacturonans (fractions II and III) were composed of galacturonic acid, arabinose, galactose and rhamnose in the relative ratios of 69:15:14:2 and 62:10:23:4, respectively. Specific rotation, FTIR, GC‐MS and NMR data revealed fraction I to be a 1→5‐α‐L arabinofuranan linked to the main chain of 1→4‐β‐D ‐galactopyranan through 1→3 linkages. The carboxyl‐reduced fraction II had 1→4‐α‐D galactopyranuronic acid residues in the main chain, which were further involved in branching through rhamnose. The striking drop in their abundance and M_r at the end of ripening, denoting depolymerization in situ, is discussed in the context of textural softening. Copyright © 2004 Society of Chemical Industry     

Physiological and biochemical response of harvested plum fruit to oxalic acid during ripening or shelf-life

The effect of oxalic acid application on plum fruit (Prunus salicina cv. ‘Damili’) ripening properties during storage or shelf-life was determined. The fruits were dipped for 3 min in solutions containing 5 mmol/L oxalic acid and then were packed into polyethylene bags and stored at 25 °C for 12 days, or at 2 °C for 20 days and subsequently at 25 °C for 12 days. Ethylene production, fruit firmness, contents of pectin and anthocyanin, specific activities of polygalacturonase (PG), pectin methylesterase (PME) and phenylalanine ammonia lyase (PAL), and chlorophyll fluorescence (Fv/Fm) were measured. The application of oxalic acid reduced ethylene production and delayed softening of plum fruit. The inhibition of softening was associated with decreased PG and PME activities; that is, the retardation of pectin solubilization/degradation. During storage or shelf-life, flesh reddening and anthocyanin synthesis were significantly inhibited in oxalic acid-treated plum fruit, accompanied with decreased PAL activity. Furthermore, it was found that variable:maximalchlorophyll fluorescence (Fv/Fm), an indicator of ripening, senescence or stress injury of fruit and vegetable, decreased much more slowly in oxalic-treated plum fruits than in control fruits. Thus, oxalic acid treatment can be an effective means to extend the shelf life of plum fruit.     

Developmental and Ripening-Related Effects on the Cell Wall of Pepino (Solanum muricatum) Fruit

Several cell wall components in ripening pepino fruit have been quantitatively and qualitatively characterised, with the aim of identifying their contributions to the loss of tissue firmness. Pepinos were graded into nine groups based on progressive, characteristic skin colour changes, previously shown to correspond with decreasing fruit firmness. While fruit softening began when the pepinos were still green but with newly acquired purple stripes, the first significant quantitative signs of cell wall modification (total pectin and hemicellulose content declining and CDTA-soluble pectin content increasing, on a fresh weight basis) were detectable later in ripening, when the fruit began to acquire yellow skin pigmentation. Gel fractionation studies demonstrated that there were increased levels of low-molecular-weight pectin and xyloglucan during pepino ripening. The change in molecular weight distribution of CDTA-soluble pectin occurred as fruit started to acquire yellow pigmentation, while xyloglucan polymers were modified at an earlier stage that coincided with the initial loss of firmness. © 1997 SCI.